Modern electronic devices are often equipped to playback multiple audio streams by mixing the output of two or more audio pipelines, also referred to as audio sources. For example, a smartphone may be configured to playback music and, at some point in time while music playback is occurring, mix in a notification sound (e.g., an incoming call sound, message waiting indicator, chat message beep, and so on). To accomplish such multi-source playback, devices can include a shared gain stage that mixes sound signals from two or more audio sources, and outputs a resulting sound signal via a speaker. Each audio source can include a number of gain stages through which an audio signal can be generated, amplified, attenuated, or otherwise processed prior to playback via a speaker. Gain stages can be implemented in various ways, and can come packaged in one or more discrete chips with varying hardware clocks, operating systems, processing priorities and scheduling.
These and other features of the present embodiments will be understood better by reading the following detailed description, taken together with the figures herein described. The accompanying drawings are not intended to be drawn to scale. In the drawings, each identical or nearly identical component that is illustrated in various figures is represented by a like numeral. For purposes of clarity, not every component may be labeled in every drawing.